The conventional semiconductor processing apparatus is constructed as shown in FIG. 1, for instance. In more detail, a plurality of process chambers 2a, 2b and 2c are arranged around a transfer chamber 1. A wafer (not shown) to be processed is carried from a process chamber to another process chamber via the transfer chamber 1 by use of a carrier robot (not shown) provided within the transfer chamber 1. A specific reaction is performed on the wafer in each of the process chambers 2a, 2b and 2c, respectively.
FIG. 2 shows a construction of each process chamber, which is composed of a chamber wall 3, a chamber cover which functions as an anode, and a wafer support base 6 which functions as a cathode. The chamber wall 3, the chamber cover 4 and the wafer support base 6 are provided with pipe lines 7a, 7b and 7c through which working fluids for controlling temperature flow, respectively. The working fluid flowing through each of these pipe lines 7a, 7b and 7c controls each temperature of the chamber wall 3, the chamber cover 4 and the wafer support base 6 to each of specific target temperatures T1, T2 and T3 separately.
The prior art temperature control system applied to the semiconductor processing apparatus, as shown in FIG. 1, comprises three temperature control machines 8a, 8b and 8c in each of which each of the target temperatures T1, T2 and T3 is set. Each of the temperature control machines 8a, 8b and 8c supplies each temperature-controlled working fluid to all of the process chambers 2a, 2b and 2c of the semiconductor processing apparatus. For instance, the first temperature control machine 8a supplies the working fluid to the chamber walls 3 of all the process chambers 2a, 2b and 2c through three pairs of fluid circulation pipes 9a, 9b; 9a, 9b; and 9a, 9b. In the same way, the second temperature control machine 8b supplies the working fluid to the chamber covers 4 of all the process chambers 2a, 2b and 2c; and the third temperature 8c supplies the working fluid to the wafer support bases 6 of all the process chambers 2a, 2b and 2c.
As shown in FIG. 3, each temperature control machine is provided with a heat exchanger 11 for cooling the working fluid, a heater 13 for heating the working fluid, and a pump 14 for circulating the temperature-controlled working fluid through the circulation pipes 9a and 9b. The heat exchanger 11 cools the working fluid by passing cooling water through a cooling water pipe 10. The heater 13 accumulates the working fluid in a tank 13a and then heats the working fluid in the tank 13a by an electric heater 12.
As described above, in the prior art temperature control system used for the semiconductor processing apparatus, one temperature control machine is used in common for a plurality of the process chambers; that is, one temperature control machine controls temperature at specific portions of a plurality of process chambers in centralization manner.
Accordingly, since the target temperature is controlled in common at the temperature-controlled portion of each of a plurality of the process chambers, it is impossible to change each target temperature at each temperature-controlled portion according to each process chamber in principle. In addition, it is also impossible to control all the temperatures of the portions of all the process chambers at the same level accurately. This is because the shape, operating condition, circulation pipe length, pressure loss, etc. differ according to each process chamber, so that the temperature of the working fluid differs slightly according to each process chamber.
Here, in order to control each target temperatures according to each process chamber, it may be possible to consider such a method of controlling the flow rate of the working fluid according to each chamber. In this method, however, since the control construction may be considerably complicated, and further since the fluid flow rate control may be interfered with each other between the process chambers, it is difficult to control the temperature accurately.
Further, in the prior temperature control system, since the centralized-control is executed, as shown in FIG. 1, the temperature control machines are inevitably located an appropriate distance apart from the semiconductor processing apparatus. As a result, the fluid circulation pipes are inevitably lengthened, and further the quantity of working fluid to be used increases. It is preferable to use as the working fluid a non-active fluid such as GALDEN (Trademark) or FLUORINERT (Trademark). However, since these non-active working fluids are considerably expensive, it is not preferable to use a large quantity of these fluid. Therefore, in the prior art temperature control system, a low-cost working fluid such as ethylene glycol or water is used, excepting special circumstances. However, since the low-cost working fluid produces ions by the influence of plasma generated within the process chamber and thereby the process chamber is easily corroded, a deionizing instrument of large size and of high cost is additionally required.
Further, in the prior art temperature control system, since the fluid circulation pipes are relatively long, the thermal loss is large in the circulation pipes. As a result, a relatively large heat capacity is necessary for each temperature control machine. In summary, the size of the prior art temperature control system is inevitably increased due to the large heat capacity and the installation place thereof.
As described above, working fluids are preferably used to control the temperatures of various objects such as a wall of a processing chamber of a semiconductor processing apparatus, air supplied to a constant temperature chamber and the like. The temperature of each working fluid must be controlled to a target temperature according to each object.
The prior art devices for controlling the temperature of the working fluid are disclosed in Japanese Published Unexamined (Kokai) Patent Application Nos. 58-219374, 7-280470, and 5-231712, for instance.
The fluid temperature control device disclosed by Japanese Published Unexamined (Kokai) Patent Application No. 58-219374 comprises a roughly cylindrical water flow passage which is partitioned finely so that water can flow in spiral state therethrough. A long and narrow electric heater is inserted into the central portion of the cylindrical water flow passage. Further, the outer circumferential surface of this cylindrical water flow passage is covered by another roughly cylindrical cooling medium flow passage which is also partitioned so that a condensed cooling medium can flow also in spiral state therethrough. Therefore, the water flowing through the water flow passage can be heated and cooled by the electric heater and the condensed cooling medium.
In the fluid temperature control device disclosed by Japanese Published Unexamined (Kokai) Patent Application No. 7-280470, an electric heater is inserted into a central portion of a pipe through which a working fluid flows, and the outer circumference of the pipe is covered by a large diameter pipe through which cooling water can flow. Therefore, the temperature of the working fluid flowing through the pipe can be controlled by the electric heater and the cooling water.
In the fluid temperature control device disclosed by Japanese Published Unexamined (Kokai) Patent Application No. 5-231712, a hollow pipe formed of quartz glass is arranged at the central portion of a cylindrical vessel through which a working fluid flows, and an infrared ray lamp is inserted into the hollow pipe. Therefore, the fluid in the vessel can be heated by the radiation heat emitted by the lamp.
In the device disclosed by Japanese Published Unexamined (Kokai) Patent Application No. 7-280470, since thermal conduction from the heater to the cooling water is utilized, there inevitably exists a non-uniforminity of the temperature of the working fluid according to the distance from the heat source. For instance, the fluid temperature is relatively high in the vicinity of the heater but low at a place remote from the heater.
In the device disclosed by Japanese Published Unexamined (Kokai) Patent Application No. 58-219374, since the fluid may be stirred when it flows helically, the non-uniformity of the fluid temperature may not occur substantially. However, since the structure of the helical flow passage is complicated, the manufacturing and maintenance process thereof is troublesome.
Further, with the devices utilizing thermal conduction, since temperature becomes locally very high in the vicinity of the heater, it is necessary to suppress the heater temperature so that the working fluid passing near the heater will not be boiled or that the heater temperature will not exceed the heat resistance limit of the materials of the heater and other vicinal elements. As a result, it is rather difficult to supply a large quantity of heat to the working fluid and further to set the target temperature of the working fluid at a high value.
The device disclosed by Japanese Published Unexamined (Kokai) Patent Application No. 5-231712 utilizes heat radiation (i.e., heat supply by electromagnetic waves, mainly by infrared rays) instead of thermal conduction. In this device, since the radiation heat of infrared rays can be emitted to all the places in the fluid uniformly, there exists no problem with respect to the non-uniformity of temperature. Further, even if the quantity of radiation heat increases, since the vicinity of the light source will not be heated up to a high temperature locally, it is possible to supply a large quantity of heat to the fluid and further to set the target temperature at a high value. With this device, however, when using as the working fluid a substance having an extremely low light absorbability, it is difficult to heat the fluid by the radiation heat.